1. Field of the invention.
The present invention relates to a roll for applicator systems for application of a medium onto a traveling material web, notably a paper or cardboard web.
2. Description of the related art.
A roll for applicator systems for application of a medium onto a traveling material web is known, e.g., from the German Patent Document No. DE 40 22 334 C2. This patent document describes a method for operation of an applicator and also illustrates an applicator roll possessing a supporting metal core with a polyurethane cover.
Known from the German Patent Document No. DE 296 09 007 U1 is a printing press roll that also features a metallic core as a support element and possesses a cover of fiber composite material.
Due to their structure with a heavy metal core, such rolls have a large inertia and, therefore, in order to achieve short start-up times, require large drive motors and heavy moving elements. Besides, due to an asymmetric structure of the roll or of the metal pipe used (e.g., due to blowhole inclusion) or due to manufacturing inaccuracies, the roll frequently fails to run smoothly, which is difficult to master by balancing. Such unstable rotation of the roll results, especially with elevated quality demands, in a non-uniform coating profile in the machine direction.
These roll configurations today achieve balance ratings of Q=1.6 up to possibly Q=1.0 with running truths up to 50 .mu.m when taking particular measures.